perf: Faster single bracket querying of a graph

R/indexing.R

@@ -53,6 +53,60 @@
 # - G[1:3,2,eid=TRUE]
 #               create an edge sequence
 
+get_adjacency_submatrix <- function(x, i, j, attr = NULL) {
+  # If i or j is NULL, assume all nodes
+  # if not NULL make sure to handle duplicates correctly
+  if (missing(i)) {
+    i_seq <- seq_len(vcount(x))
+    has_i <- FALSE
+  } else{
+    i_seq <- i
+    has_i <- TRUE
+  }
+  if (missing(j)) {
+    j_seq <- seq_len(vcount(x))
+    has_j <- FALSE
+  } else {
+    j_seq <- j
+    has_j <- TRUE
+  }
+
+  adj <- adjacent_vertices(x, i_seq, mode = "out")
+  i_degree <- map_int(adj, length)
+
+  from_id <- rep(i_seq, i_degree)
+  to_id <- unlist(adj)
+
+  edge_list <- data.frame(from = as.integer(from_id), to = as.integer(to_id))
+  if(has_j){
+    edge_list <- edge_list[edge_list$to %in% j_seq, ]
+  }
+
+  row_indices <- edge_list[[1]]
+  col_indices <- edge_list[[2]]
+
+  values <- if (is.null(attr)) {
+    1
+  } else {
+    valid_edges <- get_edge_ids(x, edge_list)
+    edge_attr(x, attr, valid_edges)
+  }
+
+  res <- Matrix::sparseMatrix(
+    i = if (has_i) match(row_indices, i_seq) else row_indices,
+    j = if (has_j) match(col_indices, j_seq) else col_indices,
+    x = values,
+    dims = c(length(i_seq), length(j_seq))
+  )
+
+  if ("name" %in% vertex_attr_names(x) && !is.null(dim(res))) {
+    rownames(res) <- vertex_attr(x, "name", i_seq)
+    colnames(res) <- vertex_attr(x, "name", j_seq)
+  }
+
+  res
+}
+
 
 #' Query and manipulate a graph as it were an adjacency matrix
 #'
@@ -151,12 +205,11 @@
 #'
 #' @method [ igraph
 #' @export
-`[.igraph` <- function(x, i, j, ..., from, to,
-                       sparse = igraph_opt("sparsematrices"),
-                       edges = FALSE, drop = TRUE,
-                       attr = if (is_weighted(x)) "weight" else NULL) {
-  ## TODO: make it faster, don't need the whole matrix usually
-
+`[.igraph` <- function(
+    x, i, j, ..., from, to,
+    sparse = igraph_opt("sparsematrices"),
+    edges = FALSE, drop = TRUE,
+    attr = if (is_weighted(x)) "weight" else NULL) {
   ################################################################
   ## Argument checks
   if ((!missing(from) || !missing(to)) &&
@@ -182,7 +235,7 @@
   ##################################################################
 
   if (!missing(from)) {
-    res <- get_edge_ids(x, rbind(from, to), error = FALSE)
+    res <- get_edge_ids(x, data.frame(from, to), error = FALSE)
     if (edges) {
       ## nop
     } else if (!is.null(attr)) {
@@ -192,32 +245,51 @@
     } else {
       res <- as.logical(res) + 0
     }
-    res
-  } else if (missing(i) && missing(j)) {
-    if (missing(edges)) {
-      as_adjacency_matrix(x, sparse = sparse, attr = attr)
-    } else {
-      as_adjacency_matrix(x, sparse = sparse, attr = attr, edges = edges)
-    }
-  } else if (missing(j)) {
-    if (missing(edges)) {
-      as_adjacency_matrix(x, sparse = sparse, attr = attr)[i, , drop = drop]
-    } else {
-      as_adjacency_matrix(x, sparse = sparse, attr = attr, edges = edges)[i, , drop = drop]
-    }
-  } else if (missing(i)) {
-    if (missing(edges)) {
-      as_adjacency_matrix(x, sparse = sparse, attr = attr)[, j, drop = drop]
-    } else {
-      as_adjacency_matrix(x, sparse = sparse, attr = attr, edges = edges)[, j, drop = drop]
+    return(res)
+  }
+
+  if (missing(i) && missing(j)) {
+    return(as_adjacency_matrix(x, sparse = sparse, attr = attr))
+  }
+
+  # convert logical, character or negative i/j to proper vertex ids
+  # also check if any vertex is duplicated and record a mapping
+  i_has_dupes <- FALSE
+  j_has_dupes <- FALSE
+
+  if (!missing(i)) {
+    i <- as_igraph_vs(x, i)
+    if (anyDuplicated(i)) {
+      i_has_dupes <- TRUE
+      i_dupl <- i
+      i <- unique(i)
+      i_map <- match(i_dupl, i)
     }
-  } else {
-    if (missing(edges)) {
-      as_adjacency_matrix(x, sparse = sparse, attr = attr)[i, j, drop = drop]
-    } else {
-      as_adjacency_matrix(x, sparse = sparse, attr = attr, edges = edges)[i, j, drop = drop]
+  }
+  if (!missing(j)) {
+    j <- as_igraph_vs(x, j)
+    if (anyDuplicated(j)) {
+      j_has_dupes <- TRUE
+      j_dupl <- j
+      j <- unique(j)
+      j_map <- match(j_dupl, j)
     }
   }
+
+  sub_adjmat <- get_adjacency_submatrix(x, i = i, j = j, attr = attr)
+  if (i_has_dupes) {
+    sub_adjmat <- sub_adjmat[i_map, , drop = FALSE]
+  }
+  if (j_has_dupes) {
+    sub_adjmat <- sub_adjmat[, j_map, drop = FALSE]
+  }
+
+  if (!sparse) {
+    as.matrix(sub_adjmat[, , drop = drop])
+  } else{
+    sub_adjmat[, , drop = drop]
+  } 
+
 }
 
 #' Query and manipulate a graph as it were an adjacency list

tests/testthat/test-indexing.R

@@ -1,4 +1,5 @@
 test_that("[ indexing works", {
+  skip_if_not_installed("Matrix", minimum_version = "1.6.0")
   g <- make_tree(20)
   ## Are these vertices connected?
   expect_equal(g[1, 2], 1)
@@ -9,6 +10,7 @@ test_that("[ indexing works", {
 })
 
 test_that("[ indexing works with symbolic names", {
+  skip_if_not_installed("Matrix", minimum_version = "1.6.0")
   g <- make_test_named_tree()
 
   expect_equal(g["a", "b"], 1)
@@ -28,6 +30,7 @@ test_that("[ indexing works with symbolic names", {
 })
 
 test_that("[ indexing works with logical vectors", {
+  skip_if_not_installed("Matrix", minimum_version = "1.6.0")
   g <- make_test_named_tree()
 
   lres <- structure(
@@ -70,6 +73,7 @@ test_that("[ indexing works with negative indices", {
 })
 
 test_that("[ indexing works with weighted graphs", {
+  skip_if_not_installed("Matrix", minimum_version = "1.6.0")
   g <- make_test_weighted_tree()
 
   expect_equal(g[1, 2], 2)
@@ -83,6 +87,7 @@ test_that("[ indexing works with weighted graphs", {
 })
 
 test_that("[ indexing works with weighted graphs and symbolic names", {
+  skip_if_not_installed("Matrix", minimum_version = "1.6.0")
   g <- make_test_weighted_tree()
 
   expect_equal(g["a", "b"], 2)
@@ -294,3 +299,49 @@ test_that("[[ handles from and to properly even if the graph has conflicting ver
   expect_true(is_igraph_vs(g[[1:3, 2:6]][[1]]))
   expect_true(is_igraph_vs(g[[from = 1:3, to = 2:6]][[1]]))
 })
+
+test_that("[ handles errors in input parameters well", {
+  g <- make_full_graph(10)
+  expect_error(g[from = 1, to = 1, i = 1, j = 1])
+  expect_error(g[from = 1])
+  expect_error(g[to = 1])
+  expect_error(g[from = NA, to = 2])
+  expect_error(g[from = 1, to = NA])
+  expect_error(g[from = 1, to = c(1, 2)])
+})
+
+test_that("[ handles all combinations of i and/or j", {
+  A <- matrix(
+    rep(
+      c(0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0),
+      c(
+        4L, 1L, 4L, 1L, 2L, 1L, 5L, 2L, 3L, 1L, 10L, 3L, 9L, 1L, 1L, 1L, 3L, 1L, 1L,
+        1L, 1L, 1L, 10L, 1L, 1L, 1L, 1L, 5L, 11L, 1L, 2L, 1L, 5L, 1L, 3L
+      )
+    ),
+    nrow = 10L,
+    ncol = 10L
+  )
+  g <- graph_from_adjacency_matrix(A, "directed")
+  expect_equal(canonicalize_matrix(g[1:3, ]), A[1:3, ])
+  expect_equal(canonicalize_matrix(g[, 4:7]), A[, 4:7])
+  expect_equal(canonicalize_matrix(g[1:3, 4:7]), A[1:3, 4:7])
+})
+
+test_that("[ handles duplicated i/j well", {
+  A <- matrix(
+    rep(
+      c(0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0),
+      c(
+        4L, 1L, 4L, 1L, 2L, 1L, 5L, 2L, 3L, 1L, 10L, 3L, 9L, 1L, 1L, 1L, 3L, 1L, 1L,
+        1L, 1L, 1L, 10L, 1L, 1L, 1L, 1L, 5L, 11L, 1L, 2L, 1L, 5L, 1L, 3L
+      )
+    ),
+    nrow = 10L,
+    ncol = 10L
+  )
+  g <- graph_from_adjacency_matrix(A, "directed")
+  expect_equal(canonicalize_matrix(g[c(1, 2, 2), ]), A[c(1, 2, 2), ])
+  expect_equal(canonicalize_matrix(g[, c(3, 3, 4, 4)]), A[, c(3, 3, 4, 4)])
+  expect_equal(canonicalize_matrix(g[c(1, 2, 2), c(3, 3, 4, 4)]), A[c(1, 2, 2), c(3, 3, 4, 4)])
+})